Low melting high lithia glass compositions and methods

ABSTRACT

The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 09/850,777,filed May 8, 2001 which is a division of U.S. application Ser. No.09/675,800, filed Sep. 28, 2000 now U.S. Pat. No. 6,258,994 B1 entitled“Methods of Vitrifying Waste With Low Melting High Lithia GlassCompositions,” which is a division of U.S. application Ser. No.09/071,853, filed May 2, 1998 now U.S. Pat. No. 6,145,343 entitled “LowMelting High Lithia Glass Compositions and Methods”.

The United States Government has rights in this invention pursuant toContract No. DEAC0989SR18035 between the U.S. Department of Energy andWestinghouse Savannah River Company.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to glass compositions suitable for use instabilization of radioactive, hazardous, or mixed waste, havingrelatively low melting points and relatively high amounts of lithia(Li₂O), to methods of making these glass compositions, and to methodsfor using the compositions to immobilize waste materials.

2. Description of the Related Art

Various hazardous, radioactive, and mixed (both hazardous andradioactive) wastes, including heavy metal wastes such as lead paint andcontaminated soils, require stabilization in solid forms that meetregulatory disposal criteria promulgated by government agencies like EPAand NRC. As discussed below, these wastes originate from a variety ofsources, and consequently can exist in a variety of forms, includingaqueous waste streams, sludge solids, mixtures of aqueous supernate andsludge solids, combinations of spent filter aids from waste watertreatment and waste sludges, supernate alone, incinerator ash,incinerator offgas blowdown, or combinations thereof, geological minetailings and sludges, asbestos, inorganic filter media, cement wasteforms in need of remediation, spent or partially spent ion exchangeresins or zeolites, contaminated soils, lead paint, etc.

Many industrial processes generate hazardous wastes in the form ofaqueous waste streams, sludge solids, aqueous supernate, incineratorash, incinerator off gas condensate, and so forth. Waste treatmentprocesses may themselves generate secondary hazardous wastes. Forexample, solids can be filtered from an aqueous waste stream by passingthe stream through filter aids, such as perlite (PERFLO) or diatomaceousearth filters. The spent filter medium is impregnated with the materialsremoved from the waste stream, such as heavy metals and other hazardousor radioactive substances. The spent filtration wastes must themselvesbe treated and stabilized before disposal. As used herein, the term“hazardous waste” includes wastes containing substances commonlyrecognized as hazardous, including but not limited to, chemical wastes,radioactive wastes, mixed chemical and radioactive wastes,heavy-metal-containing wastes, and hazardous organics.

Stabilizing hazardous wastes using currently available technology isexpensive and requires enormous resources of equipment and personnel.Stabilization processes must be operated within guidelines establishedunder the Resource Conservation and Recovery Act (RCRA), and thestabilized product must meet stringent state and federal standards. Inthe case of radioactive or mixed wastes, the stabilized wastes mustoften be stored for long periods of time waiting for decay of theradioactive components before transportation to an approved undergroundrepository. Minimizing the waste volume is important in minimizingstorage, transportation, and final disposal costs.

Incinerators are often used to destroy the hazardous constituents ofsolid and liquid wastes, as well as municipal garbage. Byproducts ofincineration include bottom ash, aqueous incinerator offgas condensate(blowdown), or mixtures of ash and offgas condensate, all of which maycontain residual hazardous and/or radioactive substances.

Radioactive waste may be further categorized into high level waste (HLW)and low level waste (LLW). High level waste is generally generated byreprocessing of spent nuclear fuel and other irradiated material,weapons production, research and development, etc. High level wasteresulting from fuel reprocessing generally is an acidic, highlyradioactive, and heat producing liquid that is generally either calcinedto a dry, granular solid or neutralized, dehydrated, and stored as adamp salt, sludge, and supernate liquid. Low level waste generallycontains more radioactivity than is allowed for municipal disposal, butare not sufficiently radioactive to produce substantial amounts of heat.Low level waste typically includes contaminated soil, clothing, gloves,resins, waste sludges, etc.

Hazardous wastes may be solidified by vitrification (incorporation intoa glass matrix) or cementation. In typical cementation processes,cement-forming materials are added to the waste; any water in the wastesolution remains in the solidified product. Therefore, the solidifiedproduct has a larger volume than the original waste solution. Also,water, including groundwater, can leach compounds out of cement overtime and cement is naturally porous, so the cement-stabilized productmust be stored in leak-proof containers to prevent leaching.

Glass is the most long-term environmentally acceptable waste form. Glassis stable and extremely durable. Moreover, the hazardous species arechemically bonded in the glass structure, forming a substantiallynonleachable composition. A number of vitrification processes forhazardous wastes have been described. Wheeler (U.S. Pat. No. 4,820,325)stabilizes toxic waste using a glass precursor material such asdiatomaceous earth mixed with a compatible glass precursor material suchas soda ash, lime (CaO) and alumina. The normally leachable toxicantbecomes fixed within the glass when the mixture is vitrified. Hayashi,et al. (U.S. Pat. No. 4,725,383) add ZnO, or a mixture of ZnO with Al₂O₃and/or CaO, to a radioactive sodium borate waste solution. The resultingmixture is dehydrated and melted to produce a vitrified solid solution.Schulz, et al. (U.S. Pat. No. 4,020,004) vitrify radioactiveferrocyanide compounds by fusion with sodium carbonate (Na₂CO₃) and amixture of basalt and B₂O₃, or silica (SiO₂) and lime (CaO).

As discussed above, solidification of these and other wastes byglassification or vitrification is known, and generally involvescombining glass forming compounds and/or natural rock, such as basaltsor nepheline syenite, with the waste materials, and melting this mixtureat temperatures sufficient to vitrify the mixture and immobilize thewaste species in the resulting glass. The waste materials becomedissolved in the melt and atomically bonded to the glass matrix thatforms when the melt is cooled.

However, vitrification processes are not perfect, and problems aresometimes experienced due to the often limited solubility of the wastematerials in the melt during glassification and/or due to the volatilityof some or all of the waste species at the relatively high temperaturesreached during the vitrification. Jantzen, “Systems Approach to NuclearWaste Glass Development,” J. Non-Cryst. Solids, 84 (1-3), 215-225, 1986.As a result, a glass forming additive that lowered the meltingtemperature of the mixture of waste and glass formers, therebydecreasing the amount or likelihood of waste volatilization, would bevery desirable. In addition, a glass forming additive that increased thesolubility of waste materials in the glass forming mixture, therebyincreasing the amount of waste atomically bonded in the glass,increasing the waste loading capacity of the glass, and decreasing thedisposal volume, would also be very desirable.

Lithia (Li₂O) has been disclosed to accelerate the dissolution of sandgrains and increase melt rate. R. M. Wiker, Glass Industry, 37, 28,(1956). Lithia has also been disclosed to have a lower volatility thansoda or potash at equal molar concentrations at 1400° C. Volf, TheChemical Approach to Glass, 1984. Lithia has been disclosed to increasethe viscosity of glass at low temperatures, N. W. Taylor et al., J.Amer. Ceram. Soc., 20, p. 296 (1937) and 24, p. 103 (1942), and todecrease the viscosity of glass at high temperatures, G. Heidtkamp etal., Glastechnick Bericht, 14, p. 99 (1936), as compared to soda (Na₂O)and potash (K₂O) containing glasses. Lithia is also disclosed toincrease the modulus of elasticity in glasses compared to soda andpotash. The mobile Li⁺ ion has also been disclosed to facilitatetransmission of electric current, so that glasses containing Li⁺ melt ata faster rate in Joule heated melters than in gas fired commercialmelters. Small amounts of Li⁺ have been disclosed to improve theelectrical resistance during glass melting, decrease glass density(since Li⁺ is a light atomic weight element), and impart a lowcoefficient of thermal expansion to the glass. Lithia is used widely inglass ceramics, such as CHEMCOR and CORNINGWARE (Corning). Volf, TheChemical Approach to Glass, 1984.

Despite all of this, lithia is not considered to be a conventional glasscomponent, and is used only for highly specialized applications in thecommercial glass industry. Lithia is used in amounts in the range ofabout 0.7 to about 1.5 wt % to improve meltability in sealing glasses,used, e.g., to seal tungsten metal to glass or to seal different typesof glass together. Lithia is also used in amounts of about 0.25 wt % toimprove meltability in glass for discharge tubes and large mirrors ofastronomical telescopes. Volf, The Chemical Approach to Glass, 1984.

One of the reasons for the failure of the art to use lithia moreextensively in glassmaking is that the production of commercialcontainer glasses, e.g., commercial bottle glass, and the production ofcommercial window glass typically does not involve the use of glassforming additives to lower the melting temperature of the glass. Themelting point of these glasses is not of great concern because there areno hazardous species to volatilize, and they are routinely formulated tomelt at temperatures of around 1300° C. to 1400° C. Lithia in particularis typically avoided in the commercial glass industry because it cancause undesirable effects, such as phase separation. Phase separationresults from inhomogeneities in the glass which form regions ofliquid-liquid immiscibility at higher temperatures that are retainedwhen the glass cools. Phase separation can result in regions that arequite small and dispersed throughout the glass, and phase separatedregions can have different optical and durability properties. W. Vogel,Chemistry of Glass, pp. 69-95, American Ceramic Society, 1985. Thesefactors can combine to make phase separated container or window glassundesirably opaque. Schott Guide to Glass.

In addition, it is often considered undesirable to mix different alkalioxides in commercial glasses due to the “mixed alkali” effect, i.e., asignificant reduction in the diffusion coefficient of the originalalkali ion due to the presence of the second alkali ion, irrespective ofthe relative size of the alkali ions. M. Hara, Ion-channel match inmixed alkali glasses, J. Non-Cryst. Solids, 131 (1991). This effect canresult in abnormal or nonlinear properties as a function of compositionfor a wide range of properties, including electrical conductivity of themelt, an important parameter in electric or Joule heated melters.

Jantzen, U.S. Pat. No. 5,102,439, disclose a borosilicate waste glasshaving about 5 wt % Li₂O produced in a melter operating at 1160° C., butdoes not suggest that the presence of lithia has any appreciable effecton the melting point of the glass. To the contrary, the nonbridgingoxygen equations described by Jantzen do not indicate that lithia hasany properties that differentiate it from other alkali metal oxides.

Lead based paint and other coatings, as discussed above, is a form ofhazardous waste subject to EPA control and regulation. Kumar et al.,U.S. Pat. No. 5,292,375, disclose a process for removal of lead basedpaint without generation of airborne particles of hazardous waste, andwithout the need to control lead-containing water solutions. In theprocess of Kumar et al., particles of a glass mixture are flame sprayedonto the coated surface to form an overlying layer of glass material. Asthis layer cools, it spalls and separates from the coated structure,taking at least some of the lead based coating with it. This can berepeated as necessary to remove the lead based coating from theunderlying structure. The spalled glass fragments can then be collected,remelted, tested for leachability and other regulatory compliance, anddisposed of in a landfill. In general, the glass fragments obtained bythe Kumar et al. process pass EPA regulations, while the materialgenerated by sandblasting lead based paint will not. The glassesdisclosed by Kumar et al. did not contain lithia or ferric oxide, andKumar et al. make no suggestion to use these compounds. However, it hasbeen disclosed that the spray properties (fluidity) and decreasedretention of lead in the structure can be enhanced by the presence ofabout 2 wt % lithia and about 12.3 wt % ferric oxide. Marra et al.,Glass Composition Development for a Thermal Spray Vitrification Process,Ceramic Trans. vol. 72, pp. 419-426, Am. Cer. Soc. (1996).

It is an object of the present invention to provide a method fordecreasing the melting point of glass compositions used to immobilizehazardous, radioactive, or mixed waste, so that hazardous or radioactivespecies are less likely to volatilize during the melting process.

It is another object of the present invention to provide a method forincreasing the solubility of hazardous or radioactive species in glasscompositions for immobilizing them, and to increase the waste loadingsof waste glass immobilization systems.

It is another object of the present invention to provide a processsuitable for disposal of radioactive and hazardous waste, such as wastesludges and supernates, spent filter aids, incinerator ash, mixtures ofincinerator ash and incinerator blowdown, geological mine tailings,asbestos, loaded ion exchange resins, contaminated soils, and lead basedpaint and other coatings.

It is another object of the present invention to provide glasscompositions that have significantly decreased melting temperatures ascompared to those compositions generally used for waste stabilization,including borosilicate glass, soda-lime-silica glass, soda-baria-silicaglass, and soda-magnesia-silica glass.

It is another object of the present invention to provide glasscompositions whose preparation reduces the occurrence of melter off-gasline pluggage, allows the use of less expensive and more robust melterdesigns, and provides longer melter design life.

It is another object of the invention to provide waste glass productionprocesses and compositions that lower vitrification temperatures,increase waste loadings, provide for large waste volume reductions, andproduce durable glasses suitable for waste stabilization and capable ofmeeting regulatory guidelines.

SUMMARY OF THE INVENTION

These and other objects and advantages are achieved by the presentinvention, which is directed to processes for lowering the vitrificationtemperature of waste glass, to processes for vitrifying radioactive,hazardous, and mixed wastes using these lowered temperatures, and toglass compositions produced by these processes.

In one sense, the present invention involves the discovery that theaddition of lithia or compounds that will form lithia undervitrification conditions, and in particular addition of lithia or lithiaformers in place of a portion of soda, or potash, or soda or potashformers, as a glass former and/or fluxing agent will significantly lowerthe melting point, and hence the vitrification temperature, of wasteglass mixtures. Because the glass melter can then be operated at asignificantly lower temperature, it is possible to contain more of thehazardous and/or radioactive species in the waste material, rather thanvolatilizing these species. Addition of lithia or lithia formers alsoincreases solubility of the species in the glass, which enhances thestabilization and retention of the species in the glass after cooling.This effect has been found to be useful in borosilicate glasses,soda-lime-silica glasses, soda-baria-silica glasses, andsoda-magnesia-silica glasses, in the presence or absence of substantialamounts of ferric oxide. The lithia may replace all or a portion of thealkali oxide glass formers typically used in these glass formingsystems. This replacement may be on a mole percent basis, or on a weightpercent basis.

Since clarity of the glass and mixed alkali effects, which are ofconcern for commercial glasses, are not of concern when stabilizingwaste in glass, lithia concentrations of between about 0.16 wt % and 11wt %, more particularly between about 0.16 wt % and about 9.30 wt %,based upon the total oxide glass formers in the glass composition, areused according to the present invention to lower the melt temperaturesof, e.g., sodium borosilicate glasses, soda-lime-silica glasses,soda-baria-silica glasses, and soda-magnesia-silica glasses for avariety of wastes, including wastes found at Savannah River Site,Fernald, Oak Ridge, Rocky Flats, and United States Army facilities.Enhanced stabilization and retention of hazardous, radioactive, andmixed waste, including heavy metals, was achieved by adding lithiumcompounds as glass formers, usually as Li₂CO₃, which converts to Li₂O inthe glass when the glass formers and waste are reacted at elevatedtemperatures.

In one embodiment, the present invention is directed to a method ofvitrifying radioactive, hazardous, or mixed waste having the steps of:

(1) mixing said waste with glass formers such that the resulting mixturecomprises SiO₂ and alkali oxide glass formers, wherein said alkali oxideglass formers comprise lithia formers and other alkali oxide glassformers in amounts such that the lithia formers, calculated as Li₂O, arefrom 11.0 wt % to about 76 wt % of the total alkali oxide glass formers,calculated as M₂O, where M is an alkali metal; and

(2) melting the resulting mixture at a temperature of between about1050° C. and about 1250° C. and cooling to form a glass composition.This mixture may be suitable for forming either an alkali oxideborosilicate glass, or an alkali oxide-lime-silica glass. As usedherein, the term alkali oxide borosilicate glass, alkalioxide-lime-silica glass, alkali oxide-baria-silica glass, or alkalioxide-magnesia-silica glass denotes a glass composition where thetypical alkali oxide, sodium oxide, has been at least partially replacedor has been supplemented by lithia. Alkali oxide borosilicate and sodaborosilicate glasses are those having a B₂O₃ content as defined in ASTMC162, i.e., 5 wt % or more B₂O₃, based upon the total weight of oxideglass formers in the glass composition (and excluding waste componentsthat are not or do not become oxide glass formers during vitrification).The terms “alkali borosilicate,” “alkali-lime-silica,”“alkali-baria-silica,” and “alkali-magnesia-silica” are synonymous withthe “alkali oxide” terms described above.

In another embodiment, the present invention is directed to a method ofdecreasing the melting point of a waste glass that contains sodiumoxide, potassium oxide, rubidium oxide, cesium oxide, or combinationsthereof and that immobilizes radioactive, hazardous, or mixed waste,having the steps of:

preparing a mixture of waste and glass formers, comprising lithia or alithia former, selected from the group consisting of Li⁻⁰ and lithiumcompounds that convert to lithia during melting at elevatedtemperatures, in an amount sufficient to provide between about 0.16 wt %and about 11 wt % Li₂O in the glass composition, based upon the totalweight of oxide glass formers in the glass composition; and

heating the mixture to a temperature below the melting point of thecorresponding mixture without said lithia or lithia former.

In another embodiment, the present invention is directed to an alkalioxide borosilicate glass composition suitable for immobilizing low levelradioactive, hazardous, or mixed waste, containing:

(a) SiO₂ in an amount ranging from about 35 wt % to about 50 wt %;

(b) B₂O₃ in an amount ranging from about 5.0 wt % to about 15 wt %;

(c) Na₂O in an amount ranging from about 9.0 wt % to about 20 wt %; and

(d) Li₂O in an amount ranging from about 4.0 wt % to about 10 wt %.

In another embodiment, the present invention is directed to an alkalioxide-lime-silica glass composition suitable for immobilizingradioactive, hazardous, or mixed waste, comprising:

(a) SiO₂ in an amount ranging from about 46 wt % to about 66 wt %;

(b) CaO in an amount ranging from about 5 wt % to about 28 wt %;

(c) Na₂O in an amount ranging from about 1.9 wt % to about 25 wt %;

(d) Li₂O in an amount ranging from about 3 wt % to about 11 wt %.

These compositions may contain an amount of B₂O₃ ranging from 0 wt % toless than 5 wt %.

In another embodiment, the present invention is directed to an alkalioxide-baria-silica glass composition suitable for immobilizingradioactive, hazardous, or mixed waste, comprising:

(a) SiO₂ in an amount ranging from about 48 wt % to about 56 wt %;

(b) BaO in an amount ranging from about 3.5 wt % to about 7.0 wt %;

(c) Na₂O in an amount ranging from about 8.0 wt % to about 15 wt %; and

(d) Li₂O in an amount ranging from about 6.0 wt % to about 10.0 wt %.

These compositions may contain an amount of B₂O₃ ranging from 0 wt % toless than 5 wt %.

In another embodiment, the present invention is directed to an alkalioxide-magnesia-silica glass composition suitable for immobilizingradioactive, hazardous, or mixed waste, comprising:

(a) SiO₂ in an amount ranging from about 40 wt % to about 68 wt %;

(b) MgO in an amount ranging from about 5.0 wt % to about 15 wt %;

(c) Na₂O in an amount ranging from about 7.0 wt % to about 20 wt %; and

(d) Li₂O in an amount ranging from about 3.0 wt % to about 9.0 wt %.

These compositions may contain an amount of B₂O₃ ranging from 0 wt % toless than 5 wt %.

The present invention can be more clearly understood from the followingdetailed description of specific embodiments thereof, which are notintended to limit the scope of the appended claims or of equivalentsthereto.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The advantages of the present invention can typically be accomplished byfirst determining the composition of the waste to be immobilized, anddetermining a suitable glass composition for this immobilization,according to techniques known to those of skill in this art. Forexample, a waste having high levels of calcium compounds like CaCO₃ orCa(OH)₂ is typically stabilized using an SLS (soda-lime-silica)composition, since the high levels of calcium compounds present in thewaste lead to high levels of lime in the glass, which is inconsistentwith soda borosilicate glasses because CaO causes borosilicate glassesto undergo phase separation. Volf, The Chemical Approach to Glass,(1984).

Once the waste composition has been determined and a typical glasscomposition selected, lithia or lithia formers are added to thecomposition in amounts ranging from 0.16 wt % to about 11 wt %, based onthe oxide glass formers in the glass composition. Typically the sodiumand/or potassium oxide glass formers necessary to obtain a particularglass composition with a given waste material are at least partiallyreplaced with the lithia or lithia formers. Replacement is typically ona mole percentage basis, but replacement on a weight percentage basismay also be used.

The mixture of waste and added glass formers is then vitrified usingstandard vitrification techniques, such as Joule melters, that are knownin the art. The mixture will melt and vitrify at a temperature belowthat at which the corresponding glass composition without the lithia orlithia formers will melt or vitrify.

In some of its specific embodiments, the present invention is directedto glass compositions within the ranges indicated below.

(1) An alkali oxide borosilicate glass composition suitable forimmobilizing low level radioactive, hazardous, or mixed waste,containing:

(a) SiO₂ in an amount ranging from about 35 wt % to about 50 wt %;

(b) B₂O₃ in an amount ranging from about 5.0 wt % to about 15 wt %;

(c) Na₂O in an amount ranging from about 9.0 wt % to about 20 wt %; and

(d) Li₂O in an amount ranging from about 4.0 wt % to about 10 wt %. Thiscomposition may also contain

(e) Al₂O₃ in an amount ranging from about 18 wt % to about 25 wt %;and/or

(f) Fe₂O₃ in an amount ranging from about 1.5 wt % to about 1.9 wt %.

For instance, this composition may more particularly contain, in wt %based on the total oxide glass formers:

SiO₂ about 39.9 to about 46.0;

B₂O₃ about 5.7 to about 9.3;

Na₂O about 9.2 to about 9.7; and

Li₂O about 4.8 to about 9.3. The composition may further contain

Al₂O₃ about 19.0 to about 21.3;

Fe₂O₃ about 1.51 to about 1.86;

CaO about 0.32 to about 0.43;

K₂O about 0.98 to about 1.53;

P₂O₅ about 1.12 to about 2.20; and/or

U₃O₈ about 0.04 to about 12, more particularly about 4.94 to about 5.25.

(2) An alkali oxide-lime-silica glass composition suitable forimmobilizing radioactive, hazardous, or mixed waste, containing:

(a) SiO₂ in an amount ranging from about 46 wt % to about 66 wt %;

(b) CaO in an amount ranging from about 5 wt % to about 28 wt %;

(c) Na₂O in an amount ranging from about 1.9 wt % to about 25 wt %;

(d) Li₂O in an amount ranging from about 3 wt % to about 11 wt %. Thiscomposition may further contain:

(e) Al₂O₃ in an amount ranging from about 2.5 wt % to about 18 wt %;

(f) Fe₂O₃ in an amount ranging from about 0.9 wt % to about 13 wt %;

(g) K₂O in an amount ranging form about 0 wt % to about 1.8 wt %;

(h) P₂O₅ in an amount ranging from about 0 wt % to about 4.5 wt %;and/or

(i) U₃O₈ in an amount ranging from about 0.5 wt % to about 12 wt %, moreparticularly about 0.5 wt % to about 5 wt %; or

(j) UO₂ in an amount ranging from about 0.4 wt % to about 12 wt %, moreparticularly about 0.4 wt % to about 0.7 wt %.

(3) An alkali oxide-baria-silica glass composition suitable forimmobilizing radioactive, hazardous, or mixed waste, containing:

(a) SiO₂ in an amount ranging from about 48 wt % to about 56 wt %;

(b) BaO in an amount ranging from about 3.5 wt % to about 7.0 wt %;

(c) Na₂O in an amount ranging from about 8.0 wt % to about 15 wt %;

(d) Li₂O in an amount ranging from about 6.0 wt % to about 10.0 wt %.The composition may also contain:

(e) Al₂O₃ in an amount ranging from about 3.0 wt % to about 5.0 wt %;

(f) PbO in an amount ranging from about 8 wt % to about 12 wt %;

(g) Fe₂O₃ in an amount ranging from about 3.0 wt % to about 5.5 wt %;

(h) CaO in an amount ranging from about 1.0 wt % to about 3.0 wt %;and/or

(i) K₂O in an amount ranging from about 0.5 wt % to about 1.0 wt %.

(4) An alkali oxide-magnesia-silica glass composition suitable forimmobilizing radioactive, hazardous, or mixed waste, containing:

(a) SiO₂ in an amount ranging from about 40 wt % to about 68 wt %;

(b) MgO in an amount ranging from about 5.0 wt % to about 15 wt %;

(c) Na₂O in an amount ranging from about 7.0 wt % to about 20 wt %; and

(d) Li₂O in an amount ranging from about 3.0 wt % to about 9.0 wt %. Thecomposition may also contain:

(e) K₂O in an amount ranging from about 0.05 wt % to about 0.2 wt %;

(f) Fe₂O₃ in an amount ranging from about 8.0 wt % to about 22 wt %;

(g) Al₂O₃ in an amount ranging from about 0.1 wt % to about 0.7 wt %;and/or

(h) CaO in an amount ranging from about 0.15 wt % to about 0.75 wt %.

EXAMPLES

The present invention has been carried out with a number of differentwastes and glass compositions. The addition of lithia or lithia formersto the glass forming mixture causes a significant reduction in themelting temperature while permitting high waste loadings, and withoutcompromising glass durability. These results are obtained in thepresence or absence of significant quantities of ferric oxide. Theconcentrations of Li₂O and Fe₂O₃ tested in the various samples is givenbelow.

Li₂O Fe₂O₃ Max. Temp. Example Site/Waste (wt %) (wt %) Reduction (° C.)1 SRS/M-Area 4.77-9.30 1.49-1.86 200 2 ORR/WETF 5.91-7.05 0.93-1.87 1773 ORR/B+C 3.0-6.0  9.38-12.51 200 4 ORR/CPCF 3.09-7.23 8.31-9.54 200 5FEMP/ 7.36-8.50 4.08-4.43 300 FERNALD 6 SRS/SOILS 11 0.75-1.21 200 7ASBESTOS 4.0-7.0  9.86-19.72 300 8 LEAD PAINT 2.0-5.0 11.3-12.3 350

The present invention is suitable for immobilization of a wide range ofwaste materials, including waste water sludge, spent filter aids, etc.As indicated below, these wastes can be immobilized using either analkali oxide borosilicate glass or an alkali oxide-lime-silica glass.When an alkali oxide borosilicate glass is used, the waste is typicallycombined into a mixture with glass formers such that the mixturecontains B₂O₃ formers in an amount sufficient to provide 5 wt % B₂O₃ ormore in the glass composition. Typically, the other alkali oxide glassformers contain Na₂O, and the lithia formers are between about 30 wt %and about 50 wt %, more particularly between about 35 wt % and about 50wt %, even more particularly between about 40 wt % and about 48 wt % ofthe alkali oxide glass formers. These glass compositions typically havea melting temperature between about 1150° C. and about 1200° C. Asindicated above, the present invention is applicable to compositionshaving amounts of ferric oxide ranging from about 0.75 wt % to about19.7 wt %, based on the total oxide glass formers in the glasscomposition, and produces glasses having melting points that are about170° C. to about 350° C., more particularly about 177° C. to about 350°C., lower than similar glasses without inclusion of lithia orreplacement of other alkali oxides, such as sodium oxide, potassiumoxide, rubidium oxide, or cesium oxide that might normally be present inthe glass composition, with lithia. These borosilicate compositions mayalso contain K₂O or Al₂O₃ or combinations thereof. In one embodiment,the invention is directed to borosilicate glass compositions thatcontain Li₂O in amounts between about 4.8 wt % and about 5.0 wt %, basedon the total oxide glass formers. This glass may contain ferric oxide inamounts less than about 2 wt % based on the total oxide glass formers.

When an alkali oxide-lime-silica glass is used, the mixture furthercontains CaO formers in an amount sufficient to provide between about0.25 wt % and about 0.5 wt % CaO in the glass composition, but themixture either does not contain B₂O₃ formers, or contains them inamounts that provide less than 5 wt % B₂O₃ in the final glasscomposition. The mixture contains other alkali glass formers such asNa₂O, and contains lithia formers in an amount between about 25 wt % andabout 35 wt %, more particularly about 30 wt %, of the alkali oxideglass formers. This composition has a melting temperature between about1150° C. and about 1250° C., more particularly about 1200° C.

Example 1 Wastewater Sludge & Contaminated (Spent) Filter Aid Wastesfrom the Savannah River Site which are Mixed (Radioactive and Hazardous)Listed Nickel Plating Line Wastes

The M-Area operations at the Savannah River Site (SRS) in Aiken, S.C.produced reactor components for nuclear weapons materials for the U.S.Department of Energy. The resulting waste is listed ResourceConservation and Recovery Act (RCRA) F006 waste which is currentlyundergoing vitrification by DOE vendor, Duratek.

Initial glass formulations were developed by C. M. Jantzen of theSavannah River Technology Center (SRTC) and J. B. Pickett of SRS/M-Area.These glass formulations included significant amounts of Li₂O to lowerthe melt temperature and allow for maximum waste loading at 1150° C.Without the addition of Li₂O, high waste loadings could both have beenachieved with this refractory waste¹ unless the waste/glass additiveswere processed at 1300-1400° C.

¹The waste is refractory due to high concentrations of Al₂O₃ and SiO₂

The M-Area waste is an example of vitrification of a mixture of wastewater sludge and contaminated filter aid. The high concentration ofspent filter aid in this waste causes the waste mixture to be high inSiO₂ and Al₂O₃, while the high sludge content causes the waste mixtureto be high in Na₂O. Because of the high SiO₂, Al₂O₃, and Na₂O content,vitrification could be realized in either the borosilicate orSoda-Lime-Silica (SLS) glass forming system. Table IA and IB givespecific examples of glasses whose melt temperature was lowered byaddition of Li₂O. Additions of 4.8-5.0 wt % Li₂O to M-Area borosilicatewaste glasses caused the melt temperature to be lowered by ˜200° C. at90% waste loading. This can be seen by comparing the composition andmelt temperature of MN-7 to MN-10 and MLSi-7 to MLSi-11A in Table IA.The durability of this waste glass, given in Table IA, as the release ofU to solution when subjected to EPA Toxic Characteristics LeachingProcedure (TCLP) was not impacted.

Likewise, when ˜5 wt % Li₂O was added to Soda-Lime-Silica (SLS) glassesthe melt temperature decreased ˜200° C. from 1400° to 1200° C. at 90 wt% waste loading. This can be seen by comparing glasses MN-23 to MN-20and MN-24 or MN-17 to MN-20 in Table IB.

Note that for all the M-Area glasses, Li₂O was substituted for Na₂O onwt % basis. Note that the waste glass compositions in Tables IA and IBcontained <2 wt % Fe₂O₃ since the M-Area waste did not containsignificant amounts of Fe₂O₃. These glasses were successfully vitrifiedin a vendor treatment facility at Savannah River Site, and were providedto the vendor on a confidential basis.

TABLE IA SRS M-AREA BOROSILICATE GLASSES MADE WITH ACTUAL WASTES² MN-7MN-10 MLSi-7 MLSi-11A GLASS OXIDE WT % WT % WT % WT % Al₂O₃ 21.6 19.024.9 21.3 B₂O₃ 5.2 5.7 5.7 9.3 CaO 0.39 0.43 0.37 0.32 Cr₂O₃ 0.07 0.100.07 0.09 Fe₂O₃ 1.71 1.86 1.49 1.51 K₂O 1.49 1.53 0.99 0.98 Li₂O 0.004.80 0.00 9.80 MgO 0.26 0.27 0.24 0.21 MnO 0.03 0.04 0.03 0.03 Na₂O 14.99.7 17.2 9.2 NiO 0.62 0.63 0.68 0.75 P₂O₅ 2.46 2.20 1.13 1.12 PbO 0.020.02 0.03 0.00 SiO₂ 45.4 46.0 37.8 39.9 TiO₂ 0.09 0.08 0.08 0.07 U₃O₈5.00 4.94 5.45 5.25 ZnO 0.03 0.03 0.03 0.03 ZrO₂ 0.01 0.02 0.02 0.02OXIDE SUM 99.28 97.35 96.21 99.51 WASTE 90 90 90 80 LOADING (Wt %) MELTTEMP 1400 1200 1400 1150 (° C.) U; TCLP, mg/L 0.63 0.60 1.30 3.10 ²Wasteglass analyses in Table IA are as analyzed.

TABLE IB SRS M-AREA SODA-LIME-SILICA GLASSES MADE WITH ACTUAL WASTE³GLASS MN-23 MN-20 MN24 MN-17 MN-20 OXIDE WT % WT % WT % WT % WT % Al₂O₃19.2 17.6 18.8 18.2 17.6 B₂0₃ 0.06 0.08 0.07 0.38 0.08 CaO 11.7 5.8 4.86.0 5.8 Cr₂O₃ 0.09 0.08 0.08 0.07 0.08 Fe₂O₃ 1.83 1.73 1.70 1.67 1.73K₂O 1.44 1.58 1.42 1.54 1.58 Li₂O 0.16 4.77 0.00 0.00 4.77 MgO 0.26 0.260.25 0.26 0.26 MnO 0.04 0.03 0.03 0.03 0.03 Na₂O 9.9 9.3 15.8 15.6 9.3NiO 0.61 .058 0.59 0.61 0.58 P₂O₅ 2.60 2.69 2.27 2.48 2.69 PbO 0.03 0.020.02 0.04 0.02 SiO₂ 46.4 46.5 45.6 47.3 46.5 TiO₂ 0.07 0.07 0.07 0.080.07 U₃O₈ 4.91 4.90 4.91 5.14 4.90 ZnO 0.03 0.03 0.03 0.03 0.03 ZrO₂0.02 0.02 0.02 0.02 0.02 OXIDE 99.35 96.03 96.42 99.41 96.03 SUM WASTE90 90 90 90 90 LOADING (Wt %) MELT 1400 1200 1400 1350 1200 TEMP (° C.)³Waste glass analyses in Table IB are as analyzed.

The present invention is also applicable to waste water sludges havinghigh levels of calcium compounds, such as those resulting from treatmentof nitrate containing wastes by biodenitrification, followed byneutralization with lime. As discussed above, because of the high limelevels in the resulting glass, this waste is not particularly suitablefor immobilization using alkali oxide borosilicate glass compositions.For this waste, the mixture typically comprises CaO formers in an amountsufficient to provide between about 12 wt % and about 30 wt % CaO in theglass composition, but either does not comprise B₂O₃ formers, orcomprises B₂O₃ formers in amounts that provide less than 5 wt % B₂O₃ inthe final glass composition. The mixture may contain other alkali glassformers comprise Na₂O, and typically contains lithia formers are betweenabout 40 wt % and about 80 wt %, more particularly between about 42 wt %and about 75 wt %, even more particularly between about 42 wt % andabout 47 wt % of the alkali oxide glass formers. Glass compositionsformed typically have melting temperatures between about 1175° C. andabout 1200° C.

Example 2 High CaO Containing Waste Water Treatment Sludge from the OakRidge Reservation (ORR) which are Mixed (Radioactive and Hazardous)Listed Wastes

The West End Treatment Facility (WETF) wastes at the Y-12 Plant at theOak Ridge Reservation (ORR) are primarily CaCO₃ resulting from treatmentof nitrate-containing wastes by biodenitrification followed byneutralization with lime. The WETF sludges are EPA RCRA listed wastesfrom treatment of solvent residues and nickel plating line waste. TheWETF sludges are primarily calcium carbonate, biomass, and ironoxyhydroxide. Depleted uranium is the primary radioisotope of concern inthis waste stream, with very low activity contributions from Tc⁹⁹ andtransuranic isotopes (Np, etc.). Phenolic compounds represent theprincipal organic hazardous constituents in the sludge.

Due to the high CaO content (CaCO₃ decomposes at the vitrificationtemperature and becomes atomically bonded in the waste glass as CaO) ofthis waste sludge, glasses should only be formulated in the SLS system.High CaO is incompatible with borosilicate glass due to the formation ofglass-in-glass phase separation which can cause the glass to beinhomogeneous and can compromise the glass durability (the glass qualityproperty of most interest when stabilizing hazardous and radioactivewastes).

For the WETF waste glasses in the SLS glass forming system, the use of5.91-8.04 wt % Li₂O lowered the melt temperatures from 1366 to 1195° C.at waste loadings varying between 20 and 40 wt % (Table II). Note thatLi₂O was substituted for Na2O in WETF 8-1 and 8-3 and 8-7 glasses butsubstituted for K₂O in WETF 8-J glass on a wt % basis.

Note that the WETF waste glasses are also low in Fe₂O₃ (<2 wt %) as arethe M-Area glasses in Example I (see Tables IA and IB). However, thewaste compositions are extremely different between Example I and ExampleII.

The Li₂O enhanced glass formulations were successfully vitrified actualWETF waste with Li₂O as a glass forming additive in a pilot scalemelter.

TABLE II OAK RIDGE RESERVATION (ORR) WEST END TREATMENT FACILITY (WETF)GLASSES (8/94)⁴ WETF WETF WETF WETF WETF WETF WETF WETF GLASS 8-1 Na 8-1Li 8-3 Na 8-3 Li 8-7 Na 8-7 Li 8-J K 8-J Li OXIDE WT % WT % WT % WT % WT% WT % WT % WT % Al₂O₃ 5.73 5.73 4.30 4.30 2.87 2.87 5.02 5.02 BaO 0.040.04 0.03 0.03 0.02 0.02 0.03 0.03 CaO 27.12 27.12 20.34 20.34 13.5613.56 23.73 23.73 Cr₂O₃ 0.04 0.04 0.03 0.03 0.02 0.02 0.03 0.03 CuO 0.070.07 0.05 0.05 0.04 0.04 0.06 0.06 Fe₂O₃ 1.87 1.87 1.40 1.40 0.93 0.931.63 1.63 K₂O 0.00 0.00 0.00 0.00 0.00 0.00 5.85 0.00 Li₂O 0.07 6.070.05 7.05 0.04 8.04 0.06 5.91 MgO 0.99 0.99 0.74 .074 0.50 0.50 4.124.12 Na₂O 14.21 8.21 15.66 8.66 17.10 9.10 1.98 1.98 NiO 0.09 0.09 0.070.07 0.04 0.04 0.08 0.08 P₂O₅ 0.56 0.56 0.42 0.42 0.28 0.28 0.49 0.49PbO 0.03 0.03 0.02 0.02 0.01 0.01 0.02 0.02 SiO₂ 48.00 48.00 56.00 56.0064.00 64.00 55.25 55.25 TiO₂ 0.00 0.00 0.00 0.00 00.00 0.00 0.65 0.65U₃O₈ 1.14 1.14 0.86 0.86 0.57 0.57 1.00 1.00 ZnO 0.03 0.03 0.03 .0030.02 0.02 0.03 0.03 OXIDE 100.00 100.00 100.00 100.00 100.00 100.00100.00 100.00 SUM WASTE 40 40 30 30 20 20 35 35 LOADING (Wt %) MELT 13661195 1366 1195 1366 1195 1366 1195 TEMP (° C.) ⁴Waste glass analyses inTable II area as targeted not as analyzed.

Other high calcium containing wastes, such as waste pond sludgecontaining Ca(OH)₂, silica, Ag, Ni, depleted U, or Tc⁹⁹ can also bevitrified using an SLS system. These wastes and the resulting glasscompositions may contain significant amounts of ferric oxide or ferricoxide formers. In this case, the mixture further contains CaO formers inan amount sufficient to provide between about 15 wt % and about 22 wt %CaO in the glass composition, and either does not contain B₂O₃ formers,or contains them in amounts that provide less than 5 wt % B₂O₃ in thefinal glass composition. The glass mixture can contain other alkaliglass formers such as Na₂O formers, and contains lithia formers arebetween about 37 wt % and about 46 wt % of said alkali oxide glassformers. The mixture can contain iron compounds sufficient to provideabout 9.0 wt % to about 13 wt % Fe₂O₃, based on the final glasscomposition. Typically the glass composition has a melting temperaturebetween about 1100° C. and about 1200° C., more particularly about 1150°C.

Example 3 High CaO Containing Waste Water Treatment Sludge from the OakRidge Reservation (ORR) which are Mixed (Radioactive and Hazardous)Listed Nickel Plating Line Wastes Containing High Fe₂O₃

The K-1407-B and K-1407-C ponds at the ORR K-25 site (formerly the OakRidge Gaseous Diffusion Plant) were used as holding and settling pondsfor various waste water treatment streams, originating from coal pilerunoff, steam plant boiler blowdown and ash treatment products,raffinate from various U recovery and equipment decontaminationoperations, plating wastes, purge cascade blowdown, and miscellaneouslaboratory wastes and chemicals. The K-1407-B pond was operated as aflow-through settling and holding pond, whereas C pond was operated as atotal containment basin, receiving dredged sludge from K-1407-B. Off-gasscrubber blowdown, ion-exchange resin, chlorides and fluorides wereadded primarily to C pond, Coal pile runoff and fly ash were addedprimarily to B pond. Stabilization efforts produced about 46,000 drums(89 and 96 gallon capacity) of cemented or partially cemented sludge.Final RCRA clean closure of these ponds entailed dredging up raw sludge(intermixed with dredge clay pond liner) and storing the waste in carbonsteel drums. This produced an additional 32,000 drums of raw sludge. Thecurrent B/C pond inventory is 7,000,000 gallons (935.000 ft³.)

The B/C Pond sludge wastes are primarily Ca(OH)₂ and SiO₂. The K-25 Pondsludges are RCRA listed mixed wastes. The primary regulatory metals ofconcern are Ag and Ni. Depleted uranium (at an average of about 0.30 wt% U-235) is the primary radioisotope of concern in this waste stream,with very low activity contributions from Tc⁹⁹.

The B/C Pond waste is different from the first two examples in thefollowing manner. The SiO₂ content of the waste is about the same as inthe Example 1 waste but much lower than the SiO₂ in the waste in Example2. At 70-80% waste loading the SiO₂ varies from 42-52 wt % in the glass.The B/C Pond waste has high Fe₂O₃ content compared to the wastes inExamples I and II. The B/C waste glasses, therefore, have high (˜12 wt%) Fe₂O₃ (Table III). The effect of Li₂O in the presence of this highFe₂O₃ content is still dramatic in lowering the melt temperatures of theglasses given in Table III by ˜200° C. This can be seen by comparingB/C-V27 to V-22, B/C-V28 to V-23, B/C-V29 to V-24. The substitutions ofLi₂O for Na₂O on a wt % basis ranged from 3.0-6.0 wt % Li₂O(See TableIII).

TABLE III OAK RIDGE RESERVATION (ORR) B/C WASTE GLASSES (1/96) B/C- B/C-B/C- B/C- B/C- B/C- GLASS V27 V22 V28 V23 V29 V24 OXIDES WT % WT % WT %WT % WT % WT % Al₂O₃ 10.18 10.18 8.91 8.91 7.64 7.64 CaO 20.62 20.6218.05 18.05 15.47 15.47 Fe₂O₃ 12.51 12.51 10.94 10.94 9.38 9.38 K₂O 1.721.72 1.50 0.00 1.29 1.29 Li₂O 3.00 0.00 4.50 0.00 6.00 0.00 Na₂O 3.006.00 4.50 9.00 6.00 12.00 NiO 0.55 0.55 0.48 0.48 0.41 0.41 SiO₂ 46.9246.92 49.81 49.81 52.69 52.69 TiO₂ 0.79 0.79 0.70 0.70 0.60 0.60 SUM99.29 99.29 99.38 99.38 99.47 99.47 WASTE 80 80 80 80 70 70 LOADING (Wt%) MELT 1150 1350 1150 1350 1150 1350 TEMP (° C.) Passed YES YES YES YESYES YES TCLP

The present invention is also useful for treating non-nitrate bearingwastes, such as plating line sludges containing significant quantitiesof organics, such as concentrated acidic or caustic wastes or oilymopwater containing beryllium, thorium, uranium, emulsified oils, soaps,cleansers, or HF scrubber solutions. The mixtures may contain ironcompounds sufficient to provide about 8 wt % to about 10 wt % Fe₂O₃,and/or phosphorus compounds sufficient to provide about 3 wt % to about5 wt % P₂O₅, based on the final glass composition. The mixtures usedfurther contain CaO formers in an amount sufficient to provide betweenabout 5 wt % and about 15 wt % CaO, more particularly between about 10wt % and about 13 wt % in the glass composition, and either do notcontain B₂O₃ formers, or contain them in amounts that provide less than5 wt % B₂O₃ in the final glass composition. The other alkali glassformers present may include Na₂O formers, and lithia formers are presentin amounts between about 11 wt % and about 50 wt %, more particularlybetween about 28 wt % and about 50 wt % of the alkali oxide glassformers. The glass compositions have melting temperatures between about1125° C. and about 1275° C., more particularly about 1150° C.

Example 4 High CaO Containing Waste Water Treatment Sludge from the OakRidge Reservation (ORR) which are Mixed (Radioactive and Hazardous)Listed Nickel Plating Line Wastes High in Organics, High in Fe₂O₃ andHigh P₂O₅

The Central Pollution Control Facility (CPCF) is designed to treatnonnitrate-bearing wastes from the Y-12 Plant including the Oak RidgeNational Laboratory (ORNL) facilities operations at Y-12. The CPCFreceives concentrated acidic or caustic wastes, and oily mopwater wastescontaining beryllium, thorium, uranium, emulsified oils, commercialsoaps or cleansers, and HF scrubber solution. The CPCF receives treatedWaste Coolant Process Facility (WCPF) and Plating Rinsewater TreatmentFacility (PRTF) wastewater effluent for final treatment and dischargewith treated CPCF wastewater effluent. The process used Ca(OH)₂ for pHadjustment and H₂SO₄ and Fe₂(SO₄)₃ for neutralization and flocculation,respectively. The CPCF currently generates waste and was designed toprocess 2.7 million gallons of wastewater per year. Historically, thefacility has operated at 50-75% of design capacity. This has producedapproximately 41,000 gallons of 5,500 ft³ (approximately 750 55-gallondrums) of CPCF sludge waste.

There are three categories of CPCF wastes, oily, wet non-oily, and drynon-oily. The CPCF wastes are RCRA listed F006 plating line sludgescontaining 20-30% organics and ˜0.40 wt % U-235. The CPCF wastes arealso listed EPA wastes. The CPCF wastes are high in SiO₂, Ca(OH)₂, andorganics. The CPCF wastes must be treed to destroy organics by eithersolvent extraction, wet oxidation, or incineration before the waste canbe vitrified in a Joule-heated melter.

Addition of 3.09 to 7.23 wt % Li₂O to the SLS glass formulationsdeveloped for the ORR CPCF waste lowered the melt temperatures ˜200° C.at waste loadings of 70-80 wt %. This can be seen by comparing glassesCPCF17 and 18, CPCF30 and 24, and CPCF28 and 24 (Table IV). The use ofthe Li₂O enabled these high waste loadings to be achieved with thisrefractory high SiO2 containing waste. Note that this waste and hencethe glasses vitrified (see Table IV) contain significant amounts ofFe₂O₃ (8.31-9.54 wt %) and P₂O₅ (3.61-4.41) compared to the glassesformulated in Examples 1 and 2. Fe₂O₃ and P205 can also lower melttemperatures but it is obvious when comparing the compositions of theglasses paired in Table IV that at constant Fe₂O₃ and P₂O₅ it is theeffect of Li₂O and not the effect of the Fe₂O₃ or P₂O₅ that is thecausative factor in lowering the melt temperatures.

TABLE IV OAK RIDGE RESERVATION (ORR) CENTRAL POLLUTION CONTROL FACILITY(CPCF) GLASSES (8/95)⁵ GLASS CPCF17 CPCF18 CPCF30 CPCF24 CPCF28 CPCF24OXIDE WT % WT % WT % WT % WT % WT % Al₂O₃ 4.73 4.73 4.12 4.12 4.12 4.12B₂O₃ 0.02 0.02 0.02 0.02 0.02 0.02 CaO 10.17 10.17 6.55 6.55 12.72 12.72Cr₂O₃ 0.12 0.12 0.10 0.10 0.10 0.10 Fe₂O₃ 9.54 9.54 8.31 8.31 8.31 8.31K₂O 0.05 0.05 0.04 0.04 0.04 0.04 Li₂O 7.23 0.00 3.09 0.00 6.17 0.00 MgO0.16 0.16 0.14 0.14 0.14 0.14 MnO 0.02 0.02 0.02 0.02 0.02 0.02 Na₂O7.58 14.81 24.99 28.08 15.73 21.91 NiO 0.16 0.16 0.14 0.14 0.14 0.14P₂O₅ 4.14 4.14 3.61 3.61 3.61 3.61 PbO 0.01 0.01 0.01 0.01 0.01 0.01SiO₂ 55.35 55.35 48.23 48.23 48.23 48.23 UO₂ 0.60 0.60 0.52 0.52 0.520.52 ZnO 0.00 0.00 0.08 0.08 0.08 0.08 OXIDE SUM 99.98 99.98 99.99 99.9999.99 99.99 WASTE 80 80 70 70 70 70 LOADING (Wt %) MELT 1250 1350 11501350 1150 1350 TEMP (° C.) Passed YES YES YES YES YES YES TCLP ⁵Wasteglass analyses in Table IV are targeted not as analyzed.

The present invention has been applied to geological mine tailingresidues containing significant quantities of heavy metal compounds,such as lead or barium compounds, using a barium oxide containing glasscomposition. These waste materials may also contain radium, uranium, oruranium daughter products (i.e., the result of fission of uranium). Themixture contains BaO formers in an amount sufficient to provide betweenabout 4 wt % and about 7 wt % BaO in the glass composition, and eitherdoes not comprise B₂O₃ formers, or comprises B₂O₃ formers in amountsthat provide less than 5 wt % B₂O₃ in the final glass composition. Otheralkali glass formers that may be present include Na₂O formers, and thelithia formers are present in amounts between about 40 wt % and about 45wt % of said alkali oxide glass formers. The mixture may also containlead compounds sufficient to provide about 8 wt % to about 12 wt % PbO,and iron compounds sufficient to provide about 3 wt % to about 6 wt %Fe₂O₃, based on the final glass composition. The resulting glasscompositions have melting temperatures between about 1000° C. and about1200° C., more particularly about 1050° C.

Example 5 High PbO, BaO, Radium Containing Geologic Mill Tailing Wastesat the Fernald Environmental Management Project (FEMP)

Vitrification is the technology that has been chosen to solidify ˜18,000tons of geologic mill tailings at the Fernald Environmental ManagementProject (FEMP) in Fernald, Ohio. The geologic mill tailings are residuesfrom the processing of pitchblende ore during 1949-1958. These wasteresidues are contained in silos in Operable Unit 4 (OU4) at the FEMPfacility. Operating Unit 4 consists of four concrete storage silos andtheir contents. Silos 1 and 2 contain K-65 mill tailing residues and abentonite cap.

The K-65 residues contain radium, uranium, uranium daughter products,and heavy metals such as lead and barium. The K-65 waste leaches lead atgreater than 100 times the allowable Environmental Protection Agency(EPA) Resource, Concentration, and Recovery Act (RCRA) concentrationlimits when tested by the Toxic Characteristic Leaching Procedure(TCLP). Vitrification is the chosen technology due to its ability tolower the release of Pb from 600 ppm from the waster to ˜1 ppm from thefinal waste glass and for its ability to contain the radium (Ra²²⁶) andits daughter product radon (Rn²²²).

Due to the high BaO content of this waste, glasses should only beformulated in the SLS system. High BaO is incompatible with borosilicateglass due to the formation of glass-in-glass phase separation which cancause the glass to be inhomogeneous and compromise the glass durability(the glass quality property of most interest when stabilizing hazardousand radioactive wastes). Previous researchers (in 1993) at the PacificNorthwest Laboratory had only been able to formulate K-65 waste glassesat high waste loadings (˜85 wt %) in the SLS system at temperaturesranging between 1350-1450° C. These high temperature glasses causevolatilization of hazardous constituents in the waste, including Se andRn²²². Melt temperatures of 1150° C. could only be achieved by the PNLresearchers at waste loadings of 50 wt %, which are inadequate to givethe volume reductions needed to make vitrification a cost effectivesolution based on waste volume reduction. Researchers at the VitreousState Laboratory had formulated glasses at waste loadings of 60-74 wt %which melted at 1050° C. but these were borosilicate glasses prone tophase separation which performed more poorly during the EPA TCLP leachtesting.

By using Li₂O containing SLS glass for the FEMP K-65 waste, the melttemperature of the waste glass was lowered from 1350° C. to 1050° C.(Table V). This lower melt temperature is necessary to reducevolatilization of hazardous selenium and Rn²²² from waste glass duringprocessing. The Li₂O containing glass is 81 wt % waste loaded comparedto the 85 wt % waste glasses developed by PNL. The targeted glasscomposition was 85 wt % waste loaded but the analyzed compositionindicated that the waste loading was more like 81 wt % waste loading.The Li₂O containing glass had a durability comparable to the highermelting PNL glass (Table V) based on the Pb release during TCLP testing.

TABLE V FERNALD ENVIRONMENTAL MANAGEMENT PROJECT (FEMP) GEOLOGIC MILLTAILINGS WASTE GLASS PNL PNL SRTC SRTC GLASS OXIDE Target As AnalyzedTarget As Analyzed Al₂O₃ 3.20 3.29 3.14 4.23 BaO 5.40 5.61 5.35 4.95 CaO1.30 1.24 1.27 1.44 Cr₂O₃ 0.00 0.00 0.00 0.14 Fe₂O₃ 4.10 4.27 4.08 4.51K₂O 0.80 0.80 0.76 0.73 Li₂O 0.00 0.00 8.50 7.92 MgO 1.50 1.51 1.44 1.63Na₂O 15.10 12.51 10.88 9.85 NiO 0.70 0.71 0.00 0.09 P₂O₅ 0.68 0.96 PbO10.60 10.95 10.45 10.30 SiO₂ 54.30 55.98 53.44 53.10 Other 3.00 3.5 0.000.00 OXIDE SUM 100.00 100.47 99.99 100.03 WASTE 85 85 81 LOADING (WT %)MELT TEMP 1350 1050 1050 (° C.) TCLP (mg/L) 0.81-1.2 1.3-1.6 for Pb

The present invention can also be used to vitrify contaminated soils andclays. Typically, an SLS glass composition is used. The glass formingmixture contains CaO formers in an amount sufficient to provide betweenabout 8 wt % and about 10 wt %, more particularly about 9 wt %, CaO inthe glass composition, and either does not comprise B₂O₃ formers, orcomprises B₂O₃ formers in amounts that provide less than 5 wt % B₂O₃ inthe final glass composition. Other alkali glass formers comprise Na₂Oformers are typically used, and the lithia formers are present inamounts sufficient to provide between about 40 wt % and about 60 wt %,more particularly about 50 wt %, of lithia based on the alkali oxideglass formers. The glass composition typically has a melting temperaturebetween about 1000° C. and about 1200° C., more particularly about 1150°C.

Example 6 Savannah River Site Contaminated Soils

Savannah River Site has many oils and clays which are contaminated withHg, pesticides, organics, etc. The soils contain 93-95 wt % SiO₂ and arevery refractory. The soils made into SLS glass by addition of 30 wt %Na₂O and CaO had to be melted at 1350° C. by substitution of half of theNa₂O by Li₂O, glasses which had similar waste loadings, e.g. 70 and 72wt %, melted at 1150° C. (Table VI). The soils did not containsignificant amounts of Fe₂O₃. Glasses formulated with additions of bothLi₂O and Fe₂O₃ to the contaminated soil also melted at temperatures of1150° C. This indicates that the presence of Li₂O and not the Fe₂O₃ wasmain contributor to the lowering of the melt temperatures. In this caseLi₂O was substituted for both CaO and SiO₂ rather than for Na₂O as inthe previous examples.

TABLE VI SAVANNAH RIVER CONTAMINATED SOILS GLASS #8 GLASS #3 GLASS OXIDE(TR96-0418)⁶ (TR95-0413)⁷ Al₂O₃ 3.02 3.60 B₂O₃ 0.00 0.02 BaO 0.00 0.01CaO 9.07 12.67 Cr₂O₃ 0.00 0.01 Fe₂O₃ 1.21 0.75 Li₂O 11 0.00 MgO 0.010.00 Na₂O 10.74 10.88 Nd₂O₃ 0.00 0.01 NiO 0.00 0.01 P₂O₅ 0.05 0.03 PbO0.00 0.03 SiO₂ 65.19 70.49 SrO 0.00 0.00 TiO₂ 0.17 0.34 ZrO₂ 0.04 0.02OXIDE SUM 100.00 98.87 WASTE LOADING 70 72 (Wt %) MELT TEMP (° C.) 11501350 ⁶Waste glass composition as targeted. ⁷Waste glass composition asanalyzed.

The present invention can also be applied to glass compositions used forimmobilizing asbestos containing waste materials. The glass formingmixture typically contains MgO formers in an amount sufficient toprovide between about 5 wt % and about 15 wt % MgO in the glasscomposition, either does not comprise B₂O₃ formers, or comprises B₂O₃formers in amounts that provide less than 5 wt % B₂O₃ in the final glasscomposition, and contains other alkali glass formers such as Na₂Oformers. The mixture may also contain iron compounds sufficient toprovide about 8 wt % to about 25 wt % Fe₂O₃, based on the final glasscomposition. The mixture contains lithia formers in amount sufficient toform between about 18 wt % and about 45 wt % lithia based on the alkalioxide glass formers. These compositions typically have a meltingtemperature between about 1000° C. and about 1200° C., more particularlyabout 1150° C.

Example 7 Asbestos Containing Material (ACM)

The safe disposal of asbestos containing materials (ACM) in the privatesector, at U.S. Department of Energy (DOE) nuclear sites, and U.S. Armyand Navy sites has become problematic. The ACM includes asbestos andfiberglass insulation, boiler lashing, transite, floor tiles, andasbestos covered pipe. The current disposal technique is to seal the ACMin plastic for safe transportation to a burial site. Burial of wrappedasbestos covered pipe necessitates large disposal volumes in regulateddisposal sites, e.g. landfills and burial grounds. The availability ofregulated disposal sites is rapidly diminishing, causing disposal to beproblematic.

Prior to World War II a family of high coefficient of expansion glasses(above 50×10⁻⁷) had been discovered. Many contained B₂O₃ in theirformulation. B₂O₃ had been used in glass formulations prior to this timedue primarily to its high cost and lack of availability. These highcoefficient of expansion glasses were known as “Palex” Type Glasses.Palex was the trade name used for the borosilicate glasses manufacturedin the Kavalier Glassworks at Sazava, Czechoslovakia around 1935. DuringWorld War II the composition was improved by adding alumina and CaOwhile decreasing the MgO content. A series of low thermal expansion (notto exceed 60×10⁻⁷) Palex type glasses with no B₂O₃ and additional MgO toreplace B₂O₃ was discovered by A. Riedel in Dolnf Polubny(Czechoslovakia) in 1939. These glasses (including Palex 5/13 in TableVII below) were produced commercially. The range of compositions ofthese glasses was given in his 1943 patent (See footnote 8 below) as amaximum of 8 wt % alkali oxides (Na₂O+K₂O), 5 wt % Al₂O₃ or ZnO, and amaximum of 15 wt % MgO. This glass was used as fire-proof and heatresistant laboratory glassware. It was the forerunner of our current dayPYREX laboratory glassware.

The Palex glass composition is advantageous for stabilization of ACMbecause most ACM material contains significant amounts of MgCO₃ andCaSO₄ used as binding materials when ACM is used to coat or insulatepipe. The Savannah River Site and many other government installationshave millions of tons of asbestos covered pipe. When the asbestos,MgCO₃, CaSO₄ material is dissolved from asbestos covered pipe it can bestabilized in Palex type glass compositions rather than in SLS orborosilicate type glass compositions. However, Palex type glasses meltin excess of 1450° C. Therefore the addition of 4-7 wt % Li₂O to replaceNa₂O and/or the K₂O in the Palex glasses was used to lower the melttemperature to 1150° C. (See Table VII).

TABLE VII ASBESTOS CONTAINING MATERIAL (ACM) GLASSES PALEX ACM GLASS⁹ACM GLASS GLASS OXIDES 5/13⁸ #4 #5 Al₂O₃ 0.00 0.43 0.22 CaO 0.00 0.740.37 Cr₂O₃ 0.00 0.30 0.15 Fe₂O₃ 0.00 19.72 9.86 K₂O 3.50 0.16 0.08 Li₂O0.00 4.00 7.00 MgO 15.00 13.71 6.86 MnO 0.00 0.17 0.09 Na₂O 3.50 17.488.74 NiO 0.00 0.13 0.07 P₂O₅ 0.00 0.06 0.03 SiO₂ 79.00 43.01 66.51 TiO₂0.00 0.06 0.03 ZnO 0.00 0.02 0.01 OXIDE SUM 101.00 100.00 100.00 WASTEN/A 60 70 LOADING (Wt %) MELT TEMP 1450 1150 1150 (° C.) ⁸O. Riedel,Fire-proof and Heat Resisting Glass, G.P. #737,033 (1943). ⁹ACM GlassCompositions given in Table VII are used as targeted.

Example 8 Pb Paint Abatement

The U.S. Army Construction Engineering Research Laboratory (USACERL) inChampaign, Ill. is developing and has patented (U.S. Pat. No. 5,292,375)a technique to thermally spray glass onto metal and wood substrates. Thehot glass vaporizes the organics in the paint and complexes with the Pbin the paint. The Pb is atomically bonded in the glass. As the glasscools it thermally contracts and spalls off the flame sprayed surface.The glass can then be swept up, remelted, tested to ensure compliancewith current EPA regulatory test limits, and then be disposed of in aland fill. This is far more effective than the current method of sandblasting the Pb paint off of tanks, ships, bridges, etc., and collectingthe Pb paint and sand which fails the current EPA regulatory test limitsand therefore needs to be stored in perpetuity.

The USACERL patented several glass compositions for their thermal sprayprogram in U.S. Pat. No. 5,292,375. None of these contained Li₂O andFe₂O₃. During a Work for Others program with SRTC, glasses containingLi₂O and Fe₂O₃ were found to have superior thermal spray properties andto atomically bond the Pb better than other glasses. These superiorproperties are due to the presence of Li₂O and Fe₂O₃ as outlined in thispatent.

TABLE VIII Glasses for Thermal Vitrification Spraying of Pb PaintUSACERL SRTC Initial Glasses Formulation (165 SRTC Optimization GLASSOXIDE Patent TDS Startup Frit) Formulation¹⁰ Al₂O₃ 0.6-4.0 4.3 5.1 B₂O₃ 1.3-25.0 7.2 10. BaO  2.0-10.0 0.00 0.00 CaO 0.5-5.5 1.4 0.00 Fe₂O₃0.00 11.3 12.3 Li₂O 0.00 5.0 2.0 MgO 0.00 0.70 0.00 MnO₂ 0.00 2.5 0.00Na₂O  5.9-10.0 11.00 16.5 NiO 0.25-0.4  0.90 0.00 SiO₂ 35.0-69.1 55.054.1 ZnO  3.0-10.0 0.00 0.00 TiO₂ 0.5-2.0 0.00 0.00 ZrO₂ 0.3-3.0 0.700.00 OXIDE SUM N/A 100 100 PbO LOADING 0.5-3.0 25.0 25.0 (Wt %) ¹⁰J. C.Marra et al., Glass Composition Development for a Thermal SprayVitrification Process, Ceramic Transactions, vol. 72, pp. 419-426(1996).

The specific embodiments of the invention having herein been described,various modifications and variations thereof well become apparent tothose of skill in the art. These modifications and variations are notintended to be excluded from the scope of the appended claims, or ofequivalents thereto.

What is claimed is:
 1. An alkali oxide-magnesia-silica glass compositionsuitable for immobilizing radioactive, hazardous, or mixed waste,comprising: (a) SiO₂ in an amount ranging from about 40 wt % to about 68wt %; (b) MgO in an amount ranging from about 5.0 wt % to about 15 wt %;(c) Na₂O in an amount ranging from about 7.0 wt % to about 20 wt %; (d)Li₂O in an amount ranging from about 3.0 wt % to about 9.0 wt %; (e) awaste loading, said waste loading being up to about 70% by wt; and (f)said loaded glass composition being opaque.
 2. The alkalioxide-magnesia-silica glass composition according to claim 1, furthercomprising: (e) K₂O in an amount ranging from about 0.05 wt % to about0.2 wt %.
 3. The alkali oxide-magnesia-silica glass compositionaccording to claim 1, further comprising: (f) Fe₂O₃ in an amount rangingfrom about 8.0 wt % to about 22 wt %.
 4. The alkalioxide-magnesia-silica glass composition according to claim 1, furthercomprising: (g) Al₂O₃ in an amount ranging from about 0.1 wt % to about0.7 wt %.
 5. The alkali oxide-magnesia-silica glass compositionaccording to claim 1, further comprising: (h) CaO in an amount rangingfrom about 0.15 wt % to about 0.75 wt %.
 6. The glass composition ofclaim 1 where the waste loading is asbestos containing material.
 7. Theglass composition of claim 1 wherein the melting point of said glass isabout 1150° C.